When marking football fields and other sports fields, manual vehicles are mostly used, which require operation by personnel during the whole marking. These vehicles often consist of 3 or 4 wheels attached to a frame, one or more containers for chalk solution attached to the frame and a guideway with control to the rate of chalking. Vehicles with 3 wheels in most cases use front wheel for direction finding, whilst vehicles with 4 wheels have typically got an attached direction finder. By often re-checking, it is in most cases possible to find direction according to the previous marking, but at longer time without marking or after periods with heavy rain, it can be necessary to place direction cords to ensure regular marking.
There are several drawbacks by manual marking.                The marking is time-consuming, especially if there has to be placed direction cords before the marking.        It is expensive in salary, in the case that volunteers can not be found.        There is risk of uneven marking, especially by circular markings.        Robot units, for instance controlled by GPS signals, have been proposed, but they have been difficult to operate, not least since paint and or chalk containers require supervision and filling, and there is risk of remains of paint or chalk, in not fully emptied containers, setting hard and thereby causing need for extensive service of the unit.        
From US 2009/0114738 is known a robot unit for marking playing fields, but this unit has no safeguard against that the used paint is exposed to oxidation, since its surface is accessible for this.
From DE9301759U1 is known a field marker, which is manually operated, and includes containers, which are replaceable. But there is no explanation of how the paint in the container is protected from oxidation. Thus, there is a risk that a not fully emptied container, if it is left in the field marking, can lead to formation of congealed paint, which again can clog pump and hose systems.